The science and effectiveness of using platelet-rich plasma derived from the patient's own blood in surgery are documented in medical, trade, and science journals. A known method for the preparation of platelets from whole blood is described in the American Association of Blood Bank's Technical Manual, 12th Edition, 1996, at pages 700-701, Method 9.11. A system employing this method collects the patient's whole blood into a collection unit with two integrally attached transfer containers. The blood is collected into the collecting container, the other two transfer containers are collapsed, and the two transfer containers with the collecting container are subjected to a “soft spin” in a centrifuge, which brings the plasma to the top of the collecting unit, leaving red cells at the bottom. In the next step, the collecting container containing the blood fractions are squeezed in a plasma extractor to force the platelet-rich plasma into one of the transfer containers through a connecting tube. A fraction comprising red cells remains behind in the collecting container, which is then removed. Next, the two transfer containers, the first being empty and the second containing the plasma, are subjected to a “heavy spin” in a centrifuge to concentrate platelets at the “bottom” of the second transfer container, leaving a platelet-poor fraction of the plasma (PPP) above the platelet concentrate (PC) in the second transfer container. The following step squeezes the second transfer container to express the PPP into the first transfer container. The platelet concentrate (PC) is then resuspended and collected for use. This system uses a process requiring six separate steps, including two centrifugal steps and two separation steps. The terms “light spin” and “heavy spin” are defined in Table 10.5-1 at page 716 of the AABB Technical Manual.
An alternative method of separating blood fractions is discussed in U.S. Pat. No. 5,102,407 and referred to as the “Amsterdam” method. Instead of two spins, soft then hard, as discussed above, a single hard spin is used in which three fractions are separated, that is, a relatively platelet-free plasma, red blood cells, and an intermediate “buffy coat” layer which contains platelets and leukocytes.
The usual procedures often employ pliable plastic bags which make it difficult to separate the blood fractions accurately. Consequently, improvements have been needed. The present invention is embodied in a new blood separation kit which provides a more convenient and efficient means for separating a patient's blood and in particular for recovering platelets.